Higher-order Zeeman effect of Mg-related donor complexes in silicon

Abstract

Magnesium (Mg) atoms in interstitial positions of a silicon host lattice form double donor centers. The binding energy of the neutral Mg 0 state corresponds to midinfrared wavelengths. Due to its interstitial character, the outer orbitals of Mg atoms can form specific bonds with different trace elements in the silicon crystal. These occur as single and double donors that become detectable by infrared spectroscopy when the concentration of either Mg or the dopant coupled to it is sufficiently large. Infrared absorption spectroscopy at high magnetic fields allows us to observe the Zeeman effect of several shallow Mg-related donor complexes and neutral Mg donors, very similar to those observed for hydrogenlike centers. The quadratic Zeeman effect indicates a hydrogenlike center structure of the excited states and spatial localization of complexes with a single excess electron in its outer shell, which are formed by Mg with an impurity atom. In contrast, Mg complexes formed by bonds with two electrons are closer to substitutional double donors in silicon.

Magnesium‐Related Donors in Silicon: State of the Art

“…In summary, it should be noted that the MIR spectra of samples unintentionally enriched with the lithium dopant reveal additional Mg‐related complexes. [ 68 ]…”

“…Another example of pairing magnesium with an interstitial impurity is the apparent formation of Mg–Li complexes that exhibit properties of H‐like shallow donors. [ 68 ] In that work, the influence of the strong magnetic field on spectra of different Mg‐related donor centers in Si:Mg was investigated.…”

“…With respect to problems of technology, the optical absorption spectroscopy at a low temperature has proven the presence of certain amounts of lithium in some n-Si:Mg samples prepared by the sandwich doping. When an initial silicon contains a significant concentration of dissolved oxygen, Li-O complexes can also be observed in samples doped with Mg. [68] Examples of such data are shown in Figure 6. The centers with the ionization energy of 32.81 meV refer to interstitial Li atoms, while donors with a slightly higher ionization energy of 39.41 meV correspond to Li-O complexes, [41,69] (note that a similar ratio of ionization energies is observed for interstitial Mg atoms and Mg-O complexes, see Section 4.4.4).…”

Infrared absorption cross sections, and oscillator strengths of interstitial and substitutional double donors in silicon

“…Low-temperature infrared absorption spectra of samples were taken with two Fourier-transform spectrometers (Bruker Vertex 80v), see for details Ref. [20]. The calibrated absorption spectra show the relevant spectral features associated with the electrically active impurity centers and indicate the strength of intracenter transitions, as well as some additional infrared-active spectral features related, e.g., to local vibrational modes of oxygen.…”

“…We followed such an assumption for calculation of donorstate wave functions and the strength of related intracenter transitions (see below). A similar effect is supposed to play a role for magnesium (Mg), which serves as an interstitial double donor in Si [20]. The concentration broadening of the spectral lines relating to double substitutional and interstitial donors in Si is also very different [5,21], which remains unexplained so far.…”